Prevent Simultaneous Package Executions

How can I prevent a package, or a section of a package, from being run more than once simultaneously? The package makes use of a staging database table, and if two copies of this package are run at the same time, there will be a race condition and possible corruption of the data in the database table. I have also noticed that the SSIS logging gets messed up and starts overwriting itself if I have more than one of these packages run at the same time.

What I am thinking of should work the same way as a serializable transaction lock on a normal query, where one query has to wait if another query has a lock on the table. I don't want the package to throw an error, I want it to wait until the other one is done.

I have been trying to use transactions in a test SSIS package, but they are not quite doing what I want them to do. I put various SSIS steps in a sequence container and require a serializable transaction. I have also tried putting the transaction at the package level, but that is not preventing simultaneous package runs.

Is there a built-in way to do this that is easy to implement? Otherwise, what I could do is insert a flag into the database indicating that a package is running, then make sure to reset the flag on any error or on completion. It seems like this alternate method could be error-prone though.

I am using SP2.